The objective for this project is to develop a tandem two-dimensional mass spectrometer that will obtain complete MS/MS information, include fragmentation ions from all precursors with their parent-daughter linkage. The ions from the ion source will not be filtered out or discriminately selected, instead each of them will be fragmented to get MS/MS spectra. The intensities of each detected ion will be stored in a two dimensional array, which coordinates m/z ratios of precursor and product ions. The scan speed of a two dimensional mass spectra frame will be equivalent to the full scan speed from a traditional quadrupole or ion trap instrument, so it will compatible for LC-2DMS methods. Development of the proposed instrument would offer a powerful analytical tool for proteomics research. For highly complex protein samples, it could provide much better peptide coverage at higher throughput, with lower detection limits, especially for low abundant proteins. Information normally from different MS/MS scan modes can be extracted from a single 2DMS scan. This would simplify some experiments, and make this instrument a versatile proteomics workstation. Although the concept of this proposed instrument uses a unique hybrid combination, most technologies applied for this instrument were developed for existing instruments. Thus, the risk of failure for this proposal is very small and the resulting benefits of this technology would have significant commercial applications. [unreadable] [unreadable]